/*
 * Copyright 2009-2010 by The Regents of the University of California
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * you may obtain a copy of the License from
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package edu.uci.ics.algebricks.compiler.algebra.properties;

import edu.uci.ics.algebricks.api.exceptions.AlgebricksException;
import edu.uci.ics.algebricks.compiler.algebra.base.LogicalVariable;
import edu.uci.ics.algebricks.compiler.algebra.operators.logical.IOperatorSchema;

public abstract class VariablePropagationPolicy {
    public static final VariablePropagationPolicy ALL = new VariablePropagationPolicy() {
        @Override
        public void propagateVariables(IOperatorSchema target, IOperatorSchema... sources) {
            int n = sources.length;
            for (int i = 0; i < n; i++) {
                target.addAllNewVariables(sources[i]);
            }
        }
    };

    public static final VariablePropagationPolicy NONE = new VariablePropagationPolicy() {
        @Override
        public void propagateVariables(IOperatorSchema target, IOperatorSchema... sources) {
            // do nothing
        }
    };

    /**
     * Adds, from each source, only variables that do not already appear in the
     * target.
     * 
     * 
     */
    public static final VariablePropagationPolicy ADDNEWVARIABLES = new VariablePropagationPolicy() {
        @Override
        public void propagateVariables(IOperatorSchema target, IOperatorSchema... sources) {
            for (IOperatorSchema s : sources) {
                for (LogicalVariable v : s) {
                    if (target.findVariable(v) < 0) {
                        target.addVariable(v);
                    }
                }
            }
        }
    };

    public abstract void propagateVariables(IOperatorSchema target, IOperatorSchema... sources)
            throws AlgebricksException;

    public static VariablePropagationPolicy concat(final VariablePropagationPolicy... policies) {
        return new VariablePropagationPolicy() {
            @Override
            public void propagateVariables(IOperatorSchema target, IOperatorSchema... sources)
                    throws AlgebricksException {
                if (policies.length != sources.length) {
                    throw new IllegalArgumentException();
                }
                for (int i = 0; i < policies.length; ++i) {
                    VariablePropagationPolicy p = policies[i];
                    IOperatorSchema s = sources[i];
                    p.propagateVariables(target, s);
                }
            }
        };
    }

}